1. Field of the Invention
This invention provides for improved methods of biodegradation of environmental pollutants. The invention specifically provides for the simultaneous treatment of the pollutants in a contaminated medium with ultraviolet radiation and lignin-degrading fungi. The fungi are discontinuously contacted with the mass of a contaminated medium. When removed from the mass of contaminated medium, the fungi and adhering contaminated medium are simultaneously exposed to the ultraviolet radiation. The combination of fungal enzymes and ultraviolet radiation enhances the rates of degradation beyond that expected for either of the treatments alone.
2. Information Disclosure
Biodegradation of persistent halogenated organic contaminants is of great interest because of its potential use to cleanup contaminated sites and industrial waste streams on-site (i.e., in situ remediation). Thomas, J. M. and Ward, C. H., In situ biorestoration of organic contaminants in the subsurface, Environ. Sci. Technol. 1989. 23:760-766; Daley, P. S., Cleaning up sites with on-site process plants, Environ. Sci. Technol. 1989. 23:912-916; Easty, D. B. and Wabers, B. A., Determination of Polychlorinated Biphenyls in Paper Mill Effluents, Tappi 61(10):71-74, 1978; and Alexander, M., Biodegradation of chemicals of environmental concern, Science, 1981. 211:132-138. Halogenated organic contaminants are known to be highly toxic. The most practical methods of degradation such as incineration are not only expensive but also known to cause secondary pollution problems. Rappe, C., Analysis of polychlorinated dioxins and furans, Environ. Sci. Technol. 1984. 18:78A-90A.
Recent studies have shown that lignin-degrading or white rot fungi such as P. chrysosporium are able to degrade a variety of highly recalcitrant and toxic compounds. Bumpus, J. A., et al., Oxidation of Persistent Environmental Pollutants Via White Rot Fungus, Science, 1985. 228:1434-1436; Aust S. D. Biodegradation of Agrochemicals By White Rot Fungi, In Recent Advances in Microbial Ecology, T. Hattori, Y. Ishda, Y. Maruyama, R. Y. Motira and A. Uchida (eds.), pp 529-533, Japan Scientific Societies Press, Tokyo, Japan; Eaton, D.C. Mineralization of Polychlorinated Biphenyls by Phanerochaete chrysosporium: a Ligninolytic Fungus, Enzyme Microb. Technol. 7:194-196; Huynh, V. et al., Dechlorination of Chloro-organics by a White Rot Fungus, Tappi Journal, 68:98-102, 1985; Mileski, G. J. et al., Biodegradation of pentachlorophenol by the White Rot Fungus Phanerochaete Chrysosporium, Appl. Environ. Microbiol. 1988, 54:2885-2889; Hammel, K. E, Kalyanaraman, B., Kirk, T. K., Oxidation of Polycyclic Aromatic Hydrocarbons and Dibenzo(p)-dioxins by Phanerochaete Chrysosporium Lignase, J. Biol. Chem. 1986. 261:16948-16952; Bumpus, J. A., Biodegradation of Polycyclic Aromatic Hydrocarbons By Phanerochaete chrysosporium, Appl. & Environ. Microbiol., 55:154-158, 1989; Eaton, T. K. et al., Fungal decoloration of Kraft Bleach Plant Effluents, Tappi 63(10):103-106, 1980; and Eaton, D.C. et al., Method Obtains Fungal Reduction of the Color of Extraction-stage Kraft Bleach Effluents, Tappi Journal, 65:89-92, 1982.
A general review of the mechanism of microbial degradation of lignin can be found in Kirk, T. K., and Farrell, R. L. Enzymatic "Combustion": The Microbial Degradation of Lignin, Ann Rev Microbiol 41:465-505, 1985.
Halogenated hydrocarbons are susceptible to photodegradation by U.V. light. Zabik, M. J. et al., Photochemistry of Bioactive compounds: a Review of Pesticide Photochemistry, Annu. Rev. Entomol. 1976. 21:61-79. It has been observed that irradiation by simulated sunlight increased the mineralization rate of 4-chlorobiphenyl in river sediment containing a mixed microbial population (Kong, H.-L., Sayler, G. S., Degradation and Total Mineralization of Monohalogenated Biphenyls in Natural Sediment and Mixed Bacterial Culture, Appl. Environ. Microbiol., 46:666-672 1983) and that microbial actions by a Pseudomonas sp. followed by subsequent irradiation by simulated sunlight degraded the yellow metabolites of 2,4-dichlorobiphenyl (i.e., sequential treatment) Baxter, R. M. and Sutherland, D. A., Biochemical and Photochemical Processes in the Degradation of Chlorinated Biphenyls Environ. Sci. Technol. 1984. 18:608-610. In another study, (Kearney P. C., et al. Oxidative Pretreatment accelerates TNT Metabolism in soils, Chemosphere, 1983. 12:1583-1597) first treated [.sup.14 C]-2,4,6-trinitrotoluene (TNT) by ultraviolet ozonation and then subjected the products to microbial degradation by Pseudomonas putida. Kearney et al. found that pretreatment by UV irradiation helped the metabolic degradation of TNT. However, there has been no successful demonstration of simultaneous application of these two technologies (i.e., use of isolated microbial and ultraviolet treatments) for the degradation of highly recalcitrant compounds.
To date no one has demonstrated that the simultaneous combination of white rot fungi and UV produce a superior means for degrading halogenated organic contaminants.